Cold Plasma Sterilization Devices and Associated Methods

ABSTRACT

A cold plasma sterilization device for sterilization of objects such as medical instruments. Gas is fed to a plasma chamber where it is energized by one or more electrodes coupled to a pulse source to thereby generate a cold plasma inside the plasma chamber. A dielectric barrier is sandwiched between the gas compartment and the electrodes to form a dielectric barrier discharge device. Inside the plasma chamber, one or more conductive stands that are coupled to ground hold the object to-be-sterilized. The cold plasma exits the plasma chamber, where it is recirculated for further use as a plasma source in subsequent cycles. Gases that can be used include noble gases such as helium, or combinations of noble gases.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application No. 61/535,250, entitled “HarmonicCold Plasma Devices and Associated Methods”, filed on Sep. 15, 2011,which is hereby expressly incorporated by reference in its entirety.

This application is related to U.S. patent application Ser. No.13/149,744, filed May 31, 2011, U.S. patent application Ser. No.12/638,161, filed Dec. 15, 2009, U.S. patent application Ser. No.12/038,159, filed Feb. 27, 2008, and U.S. Provisional Application No.60/913,369, filed Apr. 23, 2007, each of which are herein incorporatedby reference in their entireties.

BACKGROUND

1. Field of the Art

The present invention relates to devices and methods for creating coldplasmas, and, more particularly, to cold plasma sterilization methodsand application devices.

2. Background Art

Atmospheric pressure hot plasmas are known to exist in nature. Forexample, lightning is an example of a DC arc (hot) plasma. Many DC arcplasma applications have been achieved in various manufacturingprocesses, for example, for use in forming surface coatings. Atmosphericpressure cold plasma processes are also known in the art. Most of the ator near atmospheric pressure cold plasma processes are known to utilizepositive to negative electrodes in different configurations, whichrelease free electrons in a noble gas medium.

Devices that use a positive to negative electrode configuration to forma cold plasma from noble gases (helium, argon, etc.) have frequentlyexhibited electrode degradation and overheating difficulties throughcontinuous device operation. The process conditions for enabling a densecold plasma electron population without electrode degradation and/oroverheating are difficult and challenging to achieve.

In another challenging area, autoclaves continue to be used forsterilization of hospital equipment, particularly surgical instruments.However, the use of autoclaves poses several disadvantages that includethe following. First, the time needed to cycle an autoclave system(e.g., up to 45 minutes for a full cycle) is substantial, and includesthe need for significant cool down time. Second, the repeatedtemperature swings are rough on equipment, and the use of steam weathersmetals. Third, autoclaves are large pieces of equipment with high upkeepcosts and frequent downtime. Finally, when a surgical instrument isdropped or otherwise contaminated in an operating room, it must be“flashed” in the autoclave. This is a short cycle (e.g. 15-20 minutes)of high heat and pressure. These surgical instruments come back to theoperating room very hot and therefore must cool prior to their use.During this time period, the patient is under anesthetic and likely hasan opened wound, with resulting increased potential complications. It istherefore desirable to have an improved method of rapidly sterilizingsurgical instruments without the undesirable heating effects, exposureto steam and length time periods associated with autoclaves.

BRIEF SUMMARY OF THE INVENTION

As noted above, autoclaves have a number of disadvantages in their usein the sterilization of medical equipment. It is therefore desirable tohave an improved method of rapidly sterilizing surgical instrumentswithout the undesirable heating effects and exposure to steam.

Non-thermal gas plasmas (i.e., cold plasmas) have been shown to beeffective at the destruction of many pathogens. In addition to theirusefulness in the destruction of pathogens, it is also desirable torecirculate the gas used for cold plasma generation. Recirculation notonly increases the efficiency of a cold plasma system, but also reducesthe operating costs of such a system. In order to achieve effectivesterilization of surfaces, and more specifically surgical instruments,contact times of several minutes may be necessary. To effect longercontact times, it is desirable to have a chamber that can contain one ormore instruments and a volume of plasma. This description embodies theconcept, in device and technique, for creating a plasma sterilizationchamber and recirculating the feed/source specialty gas which wouldotherwise be lost to ambient air conditions. The contained CPrecirculation unit shows how a noble gas can be used repeatedly in acold plasma reaction chamber by way of electron separation in thereaction chamber, and electron attraction back to the normal atomicorbit in the non-energized part of the recirculation unit. This systemworks at or near atmospheric pressure levels, requiring no substantialadditional pressure or vacuum.

An embodiment of a cold plasma sterilization device is described thatincludes a plasma chamber having a gas input port and a gas output portfor throughput of a gas. One or more dielectric barrier dischargedevices are attached to the plasma chamber and are configured togenerate a cold plasma within the plasma chamber. Each of the one ormore dielectric barrier discharge devices is formed by a dielectricbarrier being sandwiched between a respective electrode and the interiorof the plasma chamber. In addition, each of the electrodes is coupled toa high voltage electric input. A conductive stand is disposed within theplasma chamber and configured to accept an object for sterilization,wherein the conductive stand is coupled to ground. In a furtherembodiment, recirculation of the gas in the cold plasma sterilizationdevice is described.

Another embodiment is described regarding a method of generating a coldplasma. An object for sterilization is placed on a conductive standinside a plasma chamber, where the conductive stand is coupled to groundand configured to accept the object for sterilization. The plasmachamber includes a gas input port and a gas exit port. Gas is receivedinto the plasma chamber via a gas input port, with the gas exiting via agas output port. The gas is energized in the plasma chamber to generatea cold plasma via one or more dielectric barrier discharge devicesattached to the plasma chamber. A dielectric barrier is sandwichedbetween an electrode and the interior of the plasma chamber to form eachof the one or more dielectric barrier discharge devices. Each of theelectrodes is coupled to a high voltage electric input.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIGS. 1A and 1B are cutaway views of the hand-held atmospheric harmoniccold plasma device, in accordance with embodiments of the presentinvention.

FIGS. 2A and 2B illustrate an embodiment of the cold plasma devicewithout magnets, in accordance with embodiments of the presentinvention.

FIG. 3 is an exemplary circuit diagram of the power supply of a coldplasma device, in accordance with embodiments of the present invention.

FIG. 4 illustrates the generation of cold plasma resulting using adielectric barrier discharge principle, in accordance with embodimentsof the present invention.

FIG. 5 illustrates a cold plasma sterilization device, in accordancewith an embodiment of the present invention.

FIG. 6 illustrates a recirculating cold plasma sterilization device, inaccordance with an embodiment of the present invention.

FIG. 7 illustrates a plasma chamber of a recirculating cold plasmasterilization device, in accordance with an embodiment of the presentinvention.

FIG. 8 illustrates the cold plasma emanating from a cold plasmasterilization device, in accordance with an embodiment of the presentinvention.

FIG. 9 illustrates the cold plasma emanating from a cold plasmasterilization device, in accordance with an embodiment of the presentinvention.

FIG. 10 illustrates a method of sterilizing an object using a coldplasma sterilization device, in accordance with an embodiment of thepresent invention.

FIG. 11 illustrates a method of sterilizing an object using a coldplasma sterilization device that uses plasma chamber purging, inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Cold temperature atmospheric pressure plasmas have attracted a greatdeal of enthusiasm and interest by virtue of their provision of plasmasat relatively low gas temperatures. The provision of a plasma at such atemperature is of interest to a variety of applications, including woundhealing, anti-bacterial processes, various other medical therapies andsterilization.

Cold Plasma Application Device

To achieve a cold plasma, a cold plasma device typically takes as inputa source of appropriate gas and a source of high voltage electricalenergy, and outputs a plasma plume. FIG. 1A illustrates such a coldplasma device. Previous work by the inventors in this research area hasbeen described in U.S. Provisional Patent Application No. 60/913,369,U.S. Non-provisional application Ser. No. 12/038,159 (that has issued asU.S. Pat. No. 7,633,231) and the subsequent continuation applications(collectively “the '369 application family”). The following paragraphsdiscuss further the subject matter from this application family further,as well as additional developments in this field.

The '369 application family describes a cold plasma device that issupplied with helium gas, connected to a high voltage energy source, andwhich results in the output of a cold plasma. The temperature of thecold plasma is approximately 65-120 degrees F. (preferably 65-99 degreesF.), and details of the electrode, induction grid and magnet structuresare described. The voltage waveforms in the device are illustrated at atypical operating point in '369 application family.

In a further embodiment to that described in the '369 application,plasma is generated using an apparatus without magnets, as illustratedin FIGS. 2A and 2B. In this magnet-free environment, the plasmagenerated by the action of the electrodes 61 is carried with the fluidflow downstream towards the nozzle 68. FIG. 2A illustrates a magnet-freeembodiment in which no induction grid is used. FIG. 2B illustrates amagnet-free embodiment in which induction grid 66 is used. FIG. 1Billustrates the same embodiment as illustrated FIG. 2B, but from adifferent view. Although these embodiments illustrate the cold plasma isgenerated from electrode 12, other embodiments do not power the coldplasma device using electrode 12, but instead power the cold plasmadevice using induction grid 66.

In both a magnet and a magnet-free embodiment, the inductance grid 66 isoptional. When inductance grid 66 is present, it provides ionizationenergy to the gas as the gas passes by. Thus, although the inductancegrid 66 is optional, its presence enriches the resulting plasma.

As noted above, the inductance grid 66 is optional. When absent, theplasma will nevertheless transit the cold plasma device and exit at thenozzle 68, although in this case, there will be no additional ionizationenergy supplied to the gas as it transits the latter stage of the coldplasma device.

As noted with respect to other embodiments, magnetic fields can be usedin conjunction with the production of cold plasmas. Where present,magnetic fields act, at least at some level, to constrain the plasma andto guide it through the device. In general, electrically chargedparticles tend to move along magnetic field lines in spiraltrajectories. As noted elsewhere, other embodiments can comprise magnetsconfigured and arranged to produce various magnetic field configurationsto suit various design considerations. For example, in one embodiment asdescribed in the previously filed '369 application family, a pair ofmagnets may be configured to give rise to magnetic fields with opposingdirections that act to confine the plasma near the inductance grid.

Cold Plasma Unipolar High Voltage Power Supply

The '369 application family also illustrates an embodiment of theunipolar high voltage power supply architecture and components usedtherein. The circuit architecture is reproduced here as FIG. 3, and thisuniversal power unit provides electrical power for a variety ofembodiments described further below. The architecture of this universalpower unit includes a low voltage timer, followed by a preamplifier thatfeeds a lower step-up voltage transformer. The lower step-up voltagetransformer in turn feeds a high frequency resonant inductor-capacitor(LC) circuit that is input to an upper step-up voltage transformer. Theoutput of the upper step-up voltage transformer provides the output fromthe unipolar high voltage power supply.

FIG. 3 also illustrates an exemplary implementation of the unipolar highvoltage power supply 310 architecture. In this implementation, a timerintegrated circuit such as a 555 timer 320 provides a low voltage pulsedsource with a frequency that is tunable over a frequency range centeredat approximately 1 kHz. The output of the 555 timer 320 is fed into apreamplifier that is formed from a common emitter bipolar transistor 330whose load is the primary winding of the lower step-up voltagetransformer 340. The collector voltage of the transistor forms theoutput voltage that is input into the lower step-up voltage transformer.The lower step-up transformer provides a magnification of the voltage tothe secondary windings. In turn, the output voltage of the lower step-upvoltage transformer is forwarded to a series combination of a highvoltage rectifier diode 350, a quenching gap 360 and finally to a seriesLC resonant circuit 370. As the voltage waveform rises, the rectifierdiode conducts, but the quench gap voltage will not have exceeded itsbreakdown voltage. Accordingly, the quench gap is an open circuit, andtherefore the capacitor in the series LC resonant circuit will chargeup. Eventually, as the input voltage waveform increases, the voltageacross the quench gap exceeds its breakdown voltage, and it arcs overand becomes a short circuit. At this time, the capacitor stops chargingand begins to discharge. The energy stored in the capacitor isdischarged via the tank circuit formed by the series LC connection.

Continuing to refer to FIG. 3, the inductor also forms the primarywinding of the upper step-up voltage transformer 340. Thus, the voltageacross the inductor of the LC circuit will resonate at the resonantfrequency of the LC circuit 370, and in turn will be further stepped-upat the secondary winding of the upper step-up voltage transformer. Theresonant frequency of the LC circuit 370 can be set to in the highkHz-low MHz range. The voltage at the secondary winding of the upperstep-up transformer is connected to the output of the power supply unitfor delivery to the cold plasma device. The typical output voltage is inthe 10-150 kV voltage range. Thus, voltage pulses having a frequency inthe high kHz-low MHz range can be generated with an adjustablerepetition frequency in the 1 kHz range. The output waveform is shapedsimilar to the acoustic waveform generated by an impulse such as a bellis struck with a hammer. Here, the impulse is provided when the sparkgap (or SCR) fires and produces the voltage pulse which causes theresonant circuits in the primary and secondary sides of the transformerto resonate at their specific resonant frequencies. The resonantfrequencies of the primary and the secondary windings are different. Asa result, the two signals mix and produce the unique ‘harmonic’ waveformseen in the transformer output. The net result of the unipolar highvoltage power supply is the production of a high voltage waveform with anovel “electrical signature,” which when combined with a noble gas orother suitable gas, produces a unique harmonic cold plasma that providesadvantageous results in wound healing, bacterial removal and otherapplications.

The quenching gap 360 is a component of the unipolar high voltage powersupply 310. It modulates the push/pull of electrical energy between thecapacitance banks, with the resulting generation of electrical energythat is rich in harmonic content. The quenching gap can be accomplishedin a number of different ways, including a sealed spark gap and anunsealed spark gap. The sealed spark gap is not adjustable, whileunsealed spark gaps can be adjustable. A sealed spark gap can berealized using, for example, a DECI-ARC 3000 V gas tube from ReynoldsIndustries, Inc. Adjustable spark gaps provide the opportunity to adjustthe output of the unipolar high voltage power supply and the intensityof the cold plasma device to which it is connected. In a furtherembodiment of the present invention that incorporates a sealed (andtherefore non-adjustable) spark gap, thereby ensuring a stable plasmaintensity.

In an exemplary embodiment of the unipolar high voltage power supply, a555 timer 320 is used to provide a pulse repetition frequency ofapproximately 150-600 Hz. As discussed above, the unipolar high voltagepower supply produces a series of spark gap discharge pulses based onthe pulse repetition frequency. The spark gap discharge pulses have avery narrow pulse width due to the extremely rapid discharge ofcapacitive stored energy across the spark gap. Initial assessments ofthe pulse width of the spark gap discharge pulses indicate that thepulse width is approximately 1 nsec. The spark gap discharge pulse traincan be described or modeled as a filtered pulse train. In particular, asimple resistor-inductor-capacitor (RLC) filter can be used to model thecapacitor, high voltage coil and series resistance of the unipolar highvoltage power supply. In one embodiment of the invention, the spark gapdischarge pulse train can be modeled as a simple modeled RLC frequencyresponse centered in the range of around 100 MHz. Based on the pulserepetition frequency of 192 Hz, straightforward signal analysisindicates that there would be approximately 2,000,000 individualharmonic components between DC and 400 MHz.

In another embodiment of the unipolar high voltage power supplydescribed above, a 556 timer or any timer circuit can be used in placeof the 555 timer 320. In comparison with the 555 timer, the 556 timerprovides a wider frequency tuning range that results in greaterstability and improved cadence of the unipolar high voltage power supplywhen used in conjunction with the cold plasma device.

Cold Plasma Sterilization Device

Devices, other than the cold plasma device illustrated above in FIG. 1,can also generate cold plasma. For example, cold plasma can also begenerated by a dielectric barrier discharge device, which relies on adifferent process to generate the cold plasma. As FIG. 4 illustrates, adielectric barrier discharge (DBD) device 400 contains one metalelectrode 410 covered by a dielectric layer 420. The electrical returnpath 430 is formed by the ground 440 that can be provided by thesubstrate undergoing the cold plasma treatment. Energy for thedielectric barrier discharge device 400 can be provided by a powersupply 450, such as that described above and illustrated in FIG. 2. Moregenerally, energy is input to the dielectric barrier discharge device inthe form of pulsed electrical voltage to form the plasma discharge. Byvirtue of the dielectric layer, the discharge is separated from themetal electrode and electrode etching is reduced. The pulsed electricalvoltage can be varied in amplitude and frequency to achieve varyingregimes of operation.

In an exemplary embodiment of the present invention, a sterilizationdevice is provided as shown in FIG. 5. Cold plasma sterilization device500 has plasma chamber 510 through which gas flow occurs. Gas enters atgas input 540 and exits at gas output 550. Plasma chamber 510 issurrounded by electrodes 520 which are connected to electrical inputline 530. Separating plasma chamber 510 from electrodes 520 is adielectric barrier 560. In order to ensure a gas-tight seal, one or moregaskets 570 can be used. This device has an elongated insulatingstructure surrounded by a conductor. Plasma chamber 510 can be made ofinsulating material, including acrylic, plastic, ceramic and the like.Similarly, dielectric barrier 560 can be made of any suitable dielectricmaterial sufficient to withstand the high voltages applied to theelectrodes. For example, dielectric barrier 560 can be made of asuitable dielectric material, such as ceramic, polytetrafluoroethylene(PTFE), quartz and the like. Plasma chamber 510 can be any shapeincluding a cylinder. Electrical input line 530 is configured to beconnected to a pulsed power supply (not shown). Pulsed power supplyprovides a source of pulsed electrical source of appropriate voltage andfrequency.

As noted above, plasma chamber 510 is a chamber in which gas of anappropriate composition can be presented for gas flow through to anoutput orifice, such as gas output 550. In a typical example, the gas ishelium. Other gases include a helium-oxygen gas combination, althoughother gases and gas combinations can be used. When electrical energy isapplied to device, a cold plasma is formed in the gas. Stray capacitancein plasma chamber 510 will flow to ground to complete the electricalcircuit and result in the formation of ionized gas or plasma (albeitsomewhat diffuse). A target object (e.g., an object to be sterilized)can be placed in an object holder within plasma chamber 510. If theobject holder has a connection, or a suitable capacitance, to ground,such a connection will result in a greater intensity of the plasma. Thecold plasma can be visual in that a non-transparent color will becomeevident upon the provision of energy to the gas. This type of coldplasma device can be used for the sterilization of surgical implants andinstruments, where a small size model is suitable for use in operatingroom, laboratory, medical office, etc., and a large size model issuitable for central sterilization processing in a hospital, medicalsupply or manufacturing facility.

Gas can be used once and released. Alternatively, the gas can be re-usedor recycled (i.e., recirculated). Advantages obtained by recirculatingthe gas include the following. First, gases, and in particular noblegases such as helium, are expensive. Second, power utilization can bereduced. Fresh gas that enters the system for the first time requireshigh energy levels to achieve ionization, while returning gas in arecirculation system retains an elevated energy level when it returns tothe plasma chamber. Consequently, recirculation allows for potentially alower power consumption. Third, certain working environments do notpermit large volumes of gas (e.g., noble gas) in a contained occupiedspace such as an operating room due to the risk of potentialsuffocation. Furthermore, when an ionized noble gas mixes with ambientair, reactive molecules such as ozone are produced, which are potentialirritants. Finally, a recirculation process causes turbulence thatensures the cold plasma is well distributed in the treatment chamber,and therefore reaches into the inner lumina of tools (e.g., cannulateddrill bits, laparoscopy tools).

In an exemplary embodiment of the present invention, a low gasconsumption embodiment 600 of the cold plasma device is illustrated inFIG. 6. Any appropriate gas can be used, with helium being a possiblegas. Gas is input to the recirculatory system via an fill port 650. Gascan be released from the recirculatory system via exit port 660. Arecirculate pump 610, such as a circulation fan, forces the gas in aclockwise direction from the fill port 650 to a plasma chamber 620,where the gas encounters one or more dielectric barrier devicestructures of the type illustrated in FIG. 5. These dielectric barrierdevice structures are coupled to one or more appropriate high voltagepulsed power sources of the type illustrated in FIG. 2 and describedabove. Gas exits from plasma chamber 620 to rejoin the recirculationloop in a clockwise fashion. Motion of the gas in a counter-clockwisefashion also falls within the scope of embodiments of the presentinvention. In the recirculatory system, the plasma-carrying gas can exitthrough an exit port 660 for possible external application to atreatment area of interest. Recirculate pump 610, such as a circulationfan, can also control the degree of ionization of the resulting plasma,as well as the timing of the sterilization of the treatment area. Viewtubes 640 can be optionally added to provide the ability to visuallyexamine the gas flow, and presence of the cold plasma. Pressure gauge630 can be optionally added to provide additional control andmeasurements of the performance of the cold plasma recirculatory system600.

A typical use model of the cold plasma sterilization system 600 isdescribed below. An object, such as a medical instrument, to besterilized is placed into plasma chamber 620. A suitable gas source,such as a noble gas source is connected to the fill port 650 and boththe fill port 650 and exit port 660 are opened until plasma chamber 620contains only noble gas. At this point, fill port 650 and exit port 660are both closed. The electrical energy is next provided to electricalinput 680, which is coupled to electrodes similar to electrodes 520illustrated in FIG. 5. The electrical energy causes cold plasma to formin plasma chamber 620. Recirculate pump 610, such as a recirculationfan, is turned on. The action of recirculate pump 610 draws some of theionized gas out of plasma chamber 620 to the left, as illustrated inFIG. 6. Some ionized gas may be visible in the left most view tube 640shown above. The plasma is returning to its ground state with increasingdistance from plasma chamber 620. The reconstituted noble gas passes byrecirculate pump 610 (i.e., recirculation fan, or other suitable pumpingmechanism), and returns to plasma chamber 620 to be ionized again. Thiscreates a continuous flow of cold plasma through plasma chamber 620which serves to increase contact between the plasma and object to besterilized (e.g., medical instrument), particularly in the inner spacesof the to-be-sterilized object, while maintaining cool temperatures. Inan embodiment, the recirculate pump 610 can be variable speed in orderto provide a variety of operating regimes commensurate with differentgas flow speeds.

Referring to FIG. 7, which shows further details of plasma chamber 620,there are six electrodes 720 placed on either side of this ionizationchamber 710, for a total of twelve electrodes 20. In other embodiments,electrodes 720 can be completely on one side of plasma chamber 620, ordivided into two or more groups of electrodes distributed eitherrandomly inside plasma chamber 620 or in distributed in a non-randomfashion inside plasma chamber 620. There are two metallic conductivestands 740 in the center of plasma chamber to receive the object to besterilized. These metallic conductive stands 740 are coupled to a groundpath. In other embodiments, electrodes 720 can be positioned equallyabout the center of metallic conductive stand 740, or center of metallicconductive stands 740, when multiple metallic conductive stands 740 arein use. When plasma chamber 620 is filled with gas via gas port 750 (gasport 760 would provide the exit port for the gas) and the energy isactivated via electrical wires 730, the energy flows through the gastoward the object to-be-sterilized to return to ground. In doing so, theenergy ionizes the gas within plasma chamber 620 and bathes the objectto-be-sterilized (e.g., medical instrument) in plasma thereby sanitizingits surfaces.

Referring to both FIGS. 6 and 7, in an exemplary embodiment of plasmachamber 610, plasma chamber 610 can be fitted with an acrylic top cover770 (e.g., seal plate), and a series of fasteners 670 that maintaincover 770 in place during operation. For example, the thickness of theacrylic top cover 770 can be 0.75″, with a series of 5/16″×6″ bolts usedas fasteners. Fasteners 670 (e.g,, bolts) are present to allow access toplasma chamber 610, but maintain positive pressure when plasma chamber610 is being purged of room air and filled with the required gas, e.g.,noble gas. A suitable hinge and latch system, studs and nuts or otherequivalent mechanisms can be used to implement fasteners 670.

FIG. 8 illustrates the internal environment of plasma chamber showingthe distal end of a cannulated acorn reamer 820, the object undergoingsterilization. Two electrodes 810 are visible in the upper portion ofthe illustration. One of the ground stands 830 holding the cannulatedacorn reamer 820 is visible to the right side of FIG. 8. The iridescentballs of light are focal energy flow from the plasma to the cannulatedacorn reamer 820, which are likely due to fine scale surfaceirregularities.

FIG. 9 illustrates a lateral view of the entire cannulated acorn reamer920 in plasma chamber 610 during system recirculation mode. The sixelectrodes 910 on one side of plasma chamber 610 are clearly visible.The more intense ionization is noted at the ground stands 930, while afine plasma covers the whole of plasma chamber 610. Without thecirculating air flow due to, for example, recirculate pump 610, thedistribution of the cold plasma would be more coarse and uneven.

In a further embodiment, plasma chambers 610 can be configured in seriesto allow multiple simultaneous objects to be sterilized in a row ofchambers, all connected to the same recirculatory gas system. A bypassport and valve assembly could accompany each chamber so that if onechamber were to be opened, the power is cut, and gas is bypassed so thatthe other chambers remain unaffected. Once closed again, the individualchamber is purged with fresh noble gas, valves opened, and it isreturned to the series. Such a multiple plasma chamber configurationwould be useful for high throughput applications.

In a still further embodiment, plasma chamber 510 can include doors orflaps at the gas input 540 and gas output 550. Before accessing plasmachamber 510, the doors or flaps can be closed on the inflow and outflowtubes of plasma chamber 510 in order to seal off the rest of the systemfrom the ambient environment. After the next item is loaded in plasmachamber 510, the chamber is purged with fresh gas, and the doors orflaps are then reopened. Using the doors or flaps, only plasma chamber510 needs to be purged and refilled with the gas, rather than the wholesystem. Alternatively, fill port 650 and exit port 660 can be locatedanywhere in the system, including at the plasma chamber 510. Therefore,instead of doors or flaps, fill port 650 and exit port 660 can be usedto purge plasma chamber 510. For example, a gas cartridge can beconnected to fill port 650 to refill plasma chamber 510. Using thisapproach, the gas in the remainder of the system (i.e., the gas that is“walled off”) would take a substantial amount of time to becomesufficiently contaminated as to adversely affect the cold plasmageneration process, and thereby require more extensive purging. Usingthe doors or flaps thereby reduces gas consumption. In a hospitalsterilization setting, small gas cartridges can be used rather thanlarge gas cylinders to supply gas to the cold plasma sterilizationsystem.

Cold Plasma Sterilization Usage Methods

FIG. 10 provides a flowchart of an exemplary method 1000 to generate acold plasma using a cold plasma treatment device, according to anembodiment of the present invention.

The process begins at step 1010. In step 1010, an object forsterilization is placed on a metal stand inside a plasma chamber,wherein the conductive stand is coupled to ground and configured toaccept an object for sterilization, and wherein the plasma chamberincludes a gas input port and a gas exit port. In an embodiment, anobject 820 is placed on a conductive stand 740 in a plasma chamber 710,having gas input and output ports 750, 760.

In step 1020, gas is received into a plasma chamber. In an embodiment, agas is received into plasma chamber 710.

In step 1030, the received gas is energized in the plasma chamber toform a cold plasma via one or more dielectric barrier discharge devicesattached to the plasma chamber, wherein each of the one or moredielectric barrier discharge devices is formed by a dielectric barrierbeing sandwiched between an electrode and the interior of the plasmachamber, and wherein each of the electrodes is coupled to a high voltageelectric input. In an embodiment, the received gas is energized inplasma chamber 710 using energy from electrodes 720 that is in turnreceived from electrical input 730. Dielectric barrier 560 is sandwichedbetween electrode 520 and plasma chamber 510.

At step 1040, method 1000 ends.

FIG. 11 provides a flowchart of an exemplary method 1100 to generate acold plasma including recirculation, using a cold plasma treatmentdevice, according to an embodiment of the present invention.

The process begins at step 1110. In step 1110, an object forsterilization is placed on a metal stand inside a plasma chamber,wherein the conductive stand is coupled to ground and configured toaccept an object for sterilization, and wherein the plasma chamberincludes a gas input port and a gas exit port. In an embodiment, anobject 820 is placed on a conductive stand 740 in a plasma chamber 710,having gas input and output ports 750, 760.

In step 1120, gas is received into a plasma chamber. In an embodiment, agas is received into plasma chamber 710.

In step 1130, the received gas is energized in the plasma chamber toform a cold plasma via one or more dielectric barrier discharge devicesattached to the plasma chamber, wherein each of the one or moredielectric barrier discharge devices is formed by a dielectric barrierbeing sandwiched between an electrode and the interior of the plasmachamber, and wherein each of the electrodes is coupled to a high voltageelectric input. In an embodiment, the received gas is energized inplasma chamber 710 using energy from electrodes 720 that is in turnreceived from electrical input 730. Dielectric barrier 560 is sandwichedbetween electrode 520 and plasma chamber 510.

In step 1140, flaps in the plasma chamber are closed to seal the plasmachamber.

In an embodiment, flaps in plasma chamber 710 are closed to therebysuspend gas recirculation.

In step 1150, the plasma chamber is purged with fresh gas. In anembodiment, plasma chamber 710 is purged with fresh gas with, forexample, the use of a gas cartridge to provide the required amount ofgas.

In step 1160, the flaps in the plasma chamber are reopened. In anembodiment, flaps in plasma chamber 710 are reopened to thereby resumegas recirculation.

In step 1170, method 1100 ends.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections may set forth one or morebut not all exemplary embodiments of the present invention ascontemplated by the inventor(s), and thus, are not intended to limit thepresent invention and the appended claims in any way.

The present invention has been described above with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the invention that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent invention. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

The breadth and scope of the present invention should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A cold plasma sterilization device comprising: aplasma chamber comprising a gas input port and a gas output port forthroughput of a gas; one or more dielectric barrier discharge devicesattached to the plasma chamber and configured to generate a cold plasmawithin the plasma chamber, wherein each of the one or more dielectricbarrier discharge devices is formed by a dielectric barrier beingsandwiched between a respective electrode and the interior of the plasmachamber, and wherein each of the electrodes is coupled to a high voltageelectric input; and a conductive stand disposed within the plasmachamber and configured to accept an object for sterilization, whereinthe conductive stand is coupled to ground.
 2. The cold plasmasterilization device of claim 1, farther comprising: a gas recirculationsystem coupled to the gas input port and the gas output port of theplasma chamber, the gas recirculation system comprising a recirculatingpump configured to recirculate the gas around the gas recirculationsystem.
 3. The cold plasma sterilization device of claim 2, furthercomprising: a fill port for introduction of the gas into the gasrecirculation system; and an exit port for exhaustion of the gas out ofthe gas recirculation system.
 4. The cold plasma sterilization device ofclaim 2, wherein the recirculation pump is a circulation fan.
 5. Thecold plasma sterilization device of claim 1, wherein the gas comprises anoble gas.
 6. The cold plasma sterilization device of claim 1, whereinthe gas comprises helium.
 7. The cold plasma sterilization device ofclaim 1, wherein the one or more dielectric barrier discharge devicesinclude a first group and a second group of dielectric barrier dischargedevices, the first and second group being located on opposing sides ofthe plasma chamber.
 8. The cold plasma sterilization device of claim 1,wherein the one or more dielectric barrier discharge devices aredistributed evenly with respect to a center of the conductive stand. 9.The cold plasma sterilization device of claim 1, wherein the conductivestand comprises two or more conductive stands, each configured to accepta respective objective for sterilization, and each coupled to ground.10. The cold plasma sterilization device of claim 1, wherein the plasmachamber further comprises: a cover having an open position and a closedposition, the open position providing external access to the conductivestand.
 11. A method comprising: placing an object for sterilization on aconductive stand inside a plasma chamber, wherein the conductive standis coupled to ground and configured to accept an object forsterilization, and wherein the plasma chamber includes a gas input portand a gas exit port; receiving a gas into the plasma chamber via a gasinput port, with the gas exiting via a gas output port; and energizingthe gas in the plasma chamber to generate a cold plasma via one or moredielectric barrier discharge devices attached to the plasma chamber,wherein each of the one or more dielectric barrier discharge devices isformed by a dielectric barrier being sandwiched between an electrode andthe interior of the plasma chamber, and wherein each of the electrodesis coupled to a high voltage electric input.
 12. The method of claim 11,further comprising: recirculating, by a recirculating pump, the gasaround a gas recirculation system, wherein the gas recirculation systemis coupled to the gas input port and the gas output port of the plasmachamber.
 13. The method of claim 12, further comprising: introducing gasinto the gas recirculation system via a fill port; and exhausting thegas out of the gas recirculation system via an exit port.
 14. The methodof claim 12, wherein the recirculating by a recirculating pump includesrecirculating by a circulation fan.
 15. The method of claim 11, whereinthe gas comprises a noble gas.
 16. The method of claim 11, wherein thegas comprises helium.
 17. The method of claim 11, wherein the energizingincludes using a first group and a second group of dielectric barrierdischarge devices, the first and second group being located on opposingsides of the plasma chamber.
 18. The method of claim 11, wherein theenergizing includes using one or more dielectric barrier dischargedevices distributed evenly with respect to a center of the conductivestand.
 19. The method of claim 11, wherein the placing an object forsterilization on a conductive stand inside a plasma chamber includesplacing two or more objects for sterilization on respective conductivestands inside the plasma chamber.
 20. The method of claim 11, whereinthe placing an object for sterilization on a conductive stand inside aplasma chamber includes accessing the conductive stand via a coverassociated with the plasma chamber, the cover having an open positionand a closed position, with the open position providing the access tothe conductive stand.
 21. The method of claim 12, further comprising:closing flaps in the plasma chamber to thereby seal the plasma chamberand suspend gas recirculation; purging the plasma chamber with freshgas; and opening the flaps in the plasma chamber to thereby resume gascirculation.